Electrolytic Production of Rancio
Flavor in Sherries M.A. JOSLYN XIDATION resulting in formathose of Allen ( 1 , 2 ) , there are very tion of acetaldehyde is an imUniversity of California. Berkeley. Calif. few authoritative descriptions, and portant factor in the producno complete chemical and microbiotion of flavor in sherry wines. Acetlogical study of the process has been aldehyde is an important flavoring constituent of the fino published. One of the earliest technical accounts of wine type of Spanish sherries (see, for example, Roques 34, 36) making in Jerez was that by Thudichum and Dupr6 (41) and is present in relatively high concentrations. Trillat which was later republished with but few changes by (4.3) reported the acetaldehyde content of 15 year old, Jerez Thudichum (40). Roques's description (36) has been widely (Spanish sherry) wine as 276 mg. per liter of free aldehyde quoted, but the more comprehensive account of de Castella and 418 mg. per liter of total aldehyde. Roques (34) found (9) has not received the attention it merits. In recent a Jerez wine to contain 199 and a Jerez amontillado 383 years the process used in the Jerez district has been dismg. per liter of total aldehyde. Kormal dry red and white cussed by Sannino (37), Wiley (47), and Cruess (13). The wines usually contain less than 50 mg. per liter even when fino type of sherry wine is made from Palomino grapes, old (11, 22, 29, 34, 44), and the acetaldehyde flavor is quite harvested a t 12.5" to 14" BB. (22.6' to 25.3" Brix). The disagreeable when it reaches 100 mg. per liter; the wine grapes are partly dried in the sun, crushed, and pressed becomes unpalatable a t 500 mg. per liter. Sweet fortified rather incompletely; particular care is taken to avoid exwines'may contain more acetaldehyde than dry wines without traction of tannin. Burnt gypsum is added to the grapes becoming disagreeable, particularly when they also contain in the press. According to most accounts, no sulfur dioxenough sulfite to combine with it (16, 22, 32). I n Jerez ide, tannin, or pure yeast is used to control the fermenta(sherry) wines the aldehyde formation is brought about by tion which takes place in oak butts of 100 Imperial gallons (454 liters) capacity. After about 2 months the young wines the activity of a film-forming yeast, whose classification in 1913 as a species of the sporulating Saccharomyces by are classified and fortified to about 15.5 per cent alcohol by Frowow-Bagreew was confirmed recently by Schanderl (38). volume. They are then stored in butts of Baltic oak so California sherries are produced from varieties of grapes not arranged as to provide for progressive fractional blending during maturation (Solera system). Accoqding to de Casused in Spain and by methods in which the oxidative changes are not controlled. tella, the wine is covered with a "flor" film during its entire sojourn in a fino Solera. Special care is taken in withdrawing Production of True Sherry Wines in Spain wine from and replenishing the casks of a fino Solera to disAlthough a number of popular accounts of the methods turb neither the film nor the lees. used in making sherry wines in Spain are available, such as The wines are allowed to age for several years during which 568
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INDUSTRIAL AND ENGINEERING CHEMISTRY
time they usually increase in alcohol content by selective evaporation of moisture and in spite of some utilization of alcohol by the film yeast. The pure type wines, withdrawn from the final stages of maturation from the Soleras, which are absolutely dry, are blended to suit the trade with sweet oloroso sherries which have not undergone the flowering, with a small quantity of the very sweet Pedro Ximenes, and, if necessary, with the highly colored vin de color.
California Sherry Wines According to the comments of Wetmore (46) and Bioletti ( 7 ) , the early California sherries differed considerably from the true Spanish sherries; the former were sweet and low in acidity, possessed a peculiar oxidized taste known as rancio, and generally contained unfermented sugar and a high percentage of alcohol. Lachman (SO) described the making of sherry type wines as follows : White must is fermented down to 4" Balling, and fortified to about 20 to 21 per cent of alcohol. It is then baked in the sun in coopera e ranging from 50 to 160 allons in a building whose roof and t%e side most exposed to &e morning sun are glass. The temperature in this style of sherry house goes as high as 140' F. (60' C.) and is kept steady by the assistance of a furnace at night. Another method of baking the wine is t o store it in a room built for that purpose, generally of brick, heated either by steam or hot air. In the latter process, it is always advisable to reach 140" F. (60" C.) at once, and when drawn off it should be cooled to about 60 F. (15.6 C.). O
The present postrepeal practice of producing sherry-type wines was described by Twight (45), Marquis ( S l ) , Cetti (lo), and others (3, 8). There is much variation in the type of wine used for sherry material, and in its heating and subsequent treatment, which results in a difference in the flavor and quality of the finished product. The fortified uncooked wine, known as sherry material, is heated usually in large redwood vats equipped with copper coils through which hot water or steam is circulated, although the old practice of heating sherry material in a room warmed by hot air is being revived. To improve its flavor, it is best aged in oak containers although sometimes oak chips and other materials are added t o the wine during the heating period (6, 10, 14, 25).* Another method used to obtain oak flavor is to store sherry material for some time in untreated white oak barrels and to add about 5 per cent by volume of the oak extract so obtained to other sherry material. The usual practice is to heat the sherry for 100 to 120 days a t 120" to 140" F., (48.9' to 60" C.). Smith (39)reported that fortified sherry material should be stored for a t least one year before it is heated. The time of cooking, as determined by taste, varies with the wine used and is longer for wines of high sugar content: Reducing Sugars Per cent 1.60 3.40 3.40 3.90
Apparently but little attention was paid in practice to the variety of grapes used, although Bioletti ( 7 ) stressed the importance of a suitable variety of grapes high in sugar and very low in acid content. He also pointed out that the oxidation and the acquirement of rancio taste are governed by time, temperature, and access of air: "The higher the temperature and the fuller the access of air, the more rapidly does the wine acquire this taste. Within certain limits, however, the slower the oxidation, the more delicate are the resulting flavors. The common practice of heating the wine to a very high temperature for a short time cannot produce high-class wines. The best method is to mature the wine in a warm cellar, or heat for several months a t a temperature not exceeding 100" F. (37.8' C.)."
Oxidation is necessary for the production of the characteristic flavoring constituents of sherry wines. One of the products of this oxidation is acetaldehyde. This is formed by the activity of aerobic film-forming yeasts in the true Jerez wines of Spain and by controlled oxidation in California sherry type wines. Although acetaldehyde is one of the products of this oxidation, the flavor produced by controlled oxidation cannot be duplicated merely by the addition of acetaldehyde to new wine or by strong oxidation such as is produced by the addition of hydrogen peroxide. Using aldehyde content as an index of oxidation, the authors found that electrolysis of
Sweet Wine in Blend Per cent 8 12 12 17
Cooking Period Dags
58 66 67 76
It has become the practice in California to use a small amount of muscat grape wine in sherries to improve their bouquet. Some wineries use dry muscat as the base for sherries (39). But little attention is paid to the question of aeration; some wineries circulate the sherry material during the heating period, and others depend on the oxygen dissolved by the wine when it is racked and filled.
Composition of California and Spanish Sherries Although several analyses of Spanish sherries are available, such as those compiled by Konig (24), by Krug (46,pages 1 The use of oak chips for wine was recently proscribed by the Bureau of Internal Revenue [Wine Rev., 5, No. 9, 26 (Sept., 1937)l.
the wine brings about a more rapid oxidation than that found in the normal sherry cooking process. The electrolytic oxidation produces flavoring constituents in the wine which closely resemble those of Spanish sherry in odor. I t also brings about a rapid blending of brandy with the wine. However, the electrolytically treated wines lack the taste of sherries because electrolysis has but little effect on the other factors concerned in the production of sherry flavor. Decreasing the extent of electrolysis and increasing the heating period are suggested to bring about a better balance among the flavoring constituents. The wine used for sherry material must be properly selected.
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TABLE I. COMPARATIVE AVERAGE ANALYSES OF IMPORTED AND DOMESTIC SHERRIES Analysis, Per Per Cent Total Volatile Total Sp. Gr Alcohol Exacid as acid as tartaric 15.6O C: by Val.’ tract Glycerol tartaric acetic acid Ash
-
Cent by Weight RePotasTotal ducing slum sulfurous sugar Protein sulfate PZOE acid Tannin
Sherry Reference Calif., exhibited at World’s Columbian Exposition of samples)” lSg3 (6 0.9987 19.59 6.05 0.511 0.555 . . . . . . 0.288 3.69 0.2532 0.0798 0.042 Krug ( 4 6 ) Calif., exhibited at Paris Exposition of 1900 (2 samples) b 0.9955 20.83 4.82 0.571 0.399 0.096 0.076 0.221 2.49 0.130 0.050 0.038 0.0028 0.037 Wiley(48) (15 0’ C.) Calif., analyses b y E. W. Hilgard (3 samples) 1.0285 17.40 7.40 0,449 ... 0.370 . . . . . . . . . . . . . . . . . . . . . . . Krug ( 4 6 ) Calif., analyses by C. A. . . . . . . . . . 0.199 1.42 Crampton ( 1 8 ) Crampton (3 samples) 0.9934 16.96 3.52 0.609 Spanish analyses Kijnii (7 analyses) by 0.9932 21.29 0.398 0.520 0.450 0 380 2 12 0.1700 . . . . . . . . . . Krug (46) AnclentSolera(2samples) 0.9987 16.5 1.765 0.468 O:i20 O:Ob7 0 548 0 177 O.’$Ol None Filandeau (17) 5 Polarization -2.20. b Analyses of ihese samples are given in grams per 100 cc. of wine instead of per cent by weight.
...
.................
....
...
72-86), and more recently by Kozak (28), most of them deal with the composition of the blended wines of commerce and not of the fino types. However, Filandeau (17) cited the analyses of two authentic samples of fmo type sherry. The average composition of the several types of sherries is given in Table I. Although the average composition of Spanish sherries of commerce is similar to that of California sherries made in the preprohibition era, the true fino sherries are drier and of lower alcohol content. Several samples of California sherries procured on the market during 1935 and 1936 were analyzed with the results given in Table 11; the analyses of three samples of Spanish sherries and of an authentic sample of old California sherry are also included. It is evident that there is a wide variation in acidity and extract, but that in general the California sherries resemble in composition the Spanish sherries sold
...
...
in San Francisco. There is a wider variation in the degree of oxidation of the sherries as shown by their aldehyde contents and by their oxidation-reduction potentials.
Flavor The flavor of Spanish fino type sherry is probably due in part to the variety of grapes used, to the nature of fermentation, to the metabolic products of film yeast, and to the long storage in specially prepared butts of Baltic oak. The yeast growing on the surface of the wine produces certain oxidative changes and forms a considerable amount of acetaldehyde. According to de Castella (9),“as the storage of the fino sherries in the Solera is continued, there occurs a gradual- increase in the alcoholic strength of wine. It finally reaches a concentration sufficient to inhibit the growth of the flor (film yeast). The wine becomes gradually darker, a t first
OF CALIFORNIA SHERRIES TABLE11. ANALYSES
Sample 1935: Fresno Tulare Lodi Lodi Lodi Napa Fresno Santa Clara Fresno 1936: Lodi Mendocino Fresno Fresno Fresno Fresno Tulare Tulare Lodi Mendocino Lod/ Lodi Lodi Fresno Lodi Lodi Mendocino Lodi Lodi Lodi
Old sherries: Calif .5 Gonzales Fino Pepe Fernandez 5
Alcohol Val. %
Volatile Total Sugar Acid as Acid as DexAcetic Tartaric Extract trose 0.405 0.465 0.354 0.375 0.397 0.552 0,374 0.400 0.352
0 . 081 0,032
.. ..
0.064 0.061 0.040 0.093 0.033 0.064 0.076 0.066
0.413 0.391 0.507 0.469 0.376 0.394 0,394 0.413 0.375 0.413 0.450 0.333 0.363 0.366 0.332 0.448 0.376 0.374 0.364 0.398
20.2 21.0 21.5 19.5
0,134 0.108 0,032 0,048
0.676 0.540 0.451
19.7 20.0 21.1 19.4 20.0 19.7 19.0 19.0 20.0 20.4 20.0 20.4 20.1
..
19:4
..
..
0.066
0.084 0.054 0.078 0.049 0.062 0.071 0.054 0.069 0.050
Sp. Gr., 20°/200 C.
0.510
0.042 4:io 5.20 3.50 5.33 4.81 4.78 5.29
..
.. .. .. .. , .
.. .. .. ..
..
.. .. .. .. .. ..
4 8 3 0 3 5
;95
3 7 3 45 3 45 3 75 2 40 3 35
4:94 4.94 4.40 2.52 3.55
....
0.033 0,064 0.033 0,070 0.053 0.053 0.024
.... .... .... .... .... .... ....
....
1.0047 0.9961 0.9977 0.9961 1.0062 0.9942 0.9961 0.9961 1.0000 0.9883 0.9961 0.9934 0.9937 1.0043 0.9934 1.0037
... ... ...
89
..
19 58 8 37 30 33 68
... ...
....
0.9979
0.0496
0.9956
5.2
48.5 4 35 86 97 86 64 70 50
0.0493
0.9866 1.0039 0.9843 0.9875
2.9 5.8 2.7 3.4
28.8 48 128 108
.... ....
: 0.0434 0.0353 0.0363 0.0528 0.0513 0.0560
4:45 1,l5 1.75
... ... ... ... ...
7.2 5.5 5.1 5.9 7.2 5.0 4.7 4.7 5.4 3.8 4.6 4.7 4.6 7.3 4.7 6.8 5.4 5.7
....
0 0383
3.20
......
Aldehyde as Acetaldehyde
pH
EH, 25OC. Mv.
..
...
Mg./liter
per 100 cc.
-Grams
0.053 0.060 0.072 0.042 0,088 0.099 0.063 0.066 0.058
18.7 2i:o 20.0 20.8 20.3 20.2 19.7 21.0
Tannin
Degrees B alli np: afterDealcoholization
....
.... ....
.... ....
...
... ...
... ... ... ...
... ...
...
..
.. ..
.. .. .. .. .. ....
.. ..
.. .. .. ..
... .. .. .. ... ...
...
... ... ... ... ... ... ... ... ...
236
3:98 3.89 3.91 3.81 3.82 3176
267 269 156 228 448 422 443 426
3.72
214
3:92
.. .. ..
... ... ...
A sample of old California sherry, stored in a cask f o r 12 years, then bottled in 1917,and stored in bottles until 1937. Furnished through the courtesy of
S. W. Harkleroad of A.,Mattei winery.
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INDUSTRIAL AND ENGINEERING CHEMISTRY
571
v e r y slowly b u t formed by the afterwards more reaction of the acetrapidly, exceedingly a l d e h y d e with old wines being of alcohol adds to the b o u q u e t of t h e a deep brown color.” During the wine, that the bitter first few years the taste may be due in part to the polycharacteristic framerized resins grant acetaldehyde formed from the altaste of the fino is retained, but evend e h y d e , and that tually it gives place some of the aldehyde combines with to a curious “bite” the coloring matter or sharpness akin and tannins to form to bitterness diffiinsoluble substances cult to define but which settle out’of well known to cont h e w i n e . I t is noisseurs of sherry. q u i t e l i k e l y that It takes from the loss in rancio t w e l v e t o fifteen taste of sherries is y e a r s , f r o m vindue to such transtage, before a wine formations of acetcan become amona l d e h y d e . It is tillado; as t h e Courtesu, Shewan-Jones, Inc. also likely t h a t length of time after GLASS-LINED TANKS IN A WINERY the film yeast may t h e disappearance produce acetals diof the flor increases. the fino charactel: gradually disappears until the wine rectly or, a t any rate, influence their formation. reaches the complete amontillado character. On further It is well known that the oxidation of wine exposed to air, storage the wine becomes stronger in alcohol, darker in particularly a t high temperatures, results in the production color, and usually distinctly bitter. At this stage the of a so-called rancio taste (6, 46). This taste may also be fino wine is quite similar to an old oloroso wine which has formed by fermentation a t high temperatures (6) or in the not “flowered,” presence of too much air (4%’)and is probably due to the A properly aged dry Spanish sherry has a peculiar, slightly accumulation of acetaldehydes in wines under such conditions. bitter hazelnut flavor (36). The acetaldehyde formed in The rancio taste produced by heating wines a t 120’ to 130”F. the early stages of storage in the Solera apparently undergoes (48.9’ to 54.4” C.) for 2 or 3 months is believed to be due several modifications, and the final flavor of the sherry is not only to oxidation but also to caramelization of part of probably due to the products of these reactions as well as the sugar (6). This rancio taste, which can be given, accordto the esters formed during or after fermentation and the ing to Bioletti (“), to almost any wine in any locality by extractives obtained from the wood. Trillat and others appropriate methods, is not the same as the sherry taste of (29, 34,35,36,43,&) have suggested that the fragrant acetal real Spanish sherries; the characteristic flavors of the latter are due to peculiarities of soil, variety of grape, and process of manufacture. However, Schanderl (38) claimed that the characteristic flavor of Spanish sherries can be imparted to any wine by inoculating it with the Spanish fdm-forming yeast, Saccharomyces cheresiensis. The present California sherries, as a whole, usually lack rancio flavor. When new they have an objectionable raw brandy flavor which is quite pronounced in wines fortified with brandy of high aldehyde content. The raw alcohol flavor is found in such sherries even after storage for three years. It has been found in this laboratory that the addition of 50 to 100 p. p. m. of sulfur dioxide to such sherries markedly reduces this objectionable flavor and aids in stabilizing them towards clouding. This effect of added sulfur dioxide is apparently due to its combination with aldehydes present. The new wines also have a sharp bitter flavor which may be due either to the addition of grape juice concentrated in an open kettle, to the addition of caramel for coloring, or to the excessive caramelization that occurs a t the surface of the copper steam coils in the usual sherry cooker. If copper salts picked up by wine heated with copper coils are not removed, they also add to the undesirable flavors.
Courtesy, Wzne Reuiew
AUXILIARY HOTWATERBOILERWITH DUALCONTROL USED BY THE COLTON WINE COMPANY
Electrolytic Heating Investigations on the aging of sherry and other wines have been under way in this laboratory for several years (14, 26).
.
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572
A number of methods for rapidly improving the flavor of sherry wines have been tested with the object of developing some standard procedure which would be applicable to all types of sherry material. Of the various treatments tested, the most satisfactory has been electrolytic heating. Although electrolytic treatment has been applied to the artificial aging of alcoholic beverages (16, ZZJ), the direct application of alternating currents to the heating of sherry material for the production of rancio flavor has not been reported. The preliminary tests were quite promising; a rapid blending of alcohol with the wine occurred even when the wine was fortified with very raw brandy. A pleasing rancio odor was obtained even after 7 days of treatment although the taste of the wine, largely owing to the poor type of sherry material used, was not very pleasing. However, on further storage in bottles the electrically treated sherries developed a satisfactory flavor. The aldehyde flavor developed quite rapidly during electrolysis with 60-cycle alternating current, and the chief difficulty experienced in using the apparatus described below was in adjusting the aldehyde formation to the slow caramelization necessary for the improvement of color and flavor. The effects obtained by electrolysis are probably due to the alternate oxidation and reduction that occurs a t the electrodes, rather than to simple oxidation, It is probable that reduction plays as important a role in the aging of wine as it apparently does in the aging of whisky
VOL. 30, NO. 5
ALCOHOL was determined by the ebullioscope on the distillate pre ared as directed by A. 0. A. C. (4). (This compares closely wit[ the official method, 16). SPECIFICGRAVITY of the wine and of the dealcoholized wine was determined at 20" C. by a Westphal Chainomatic balance, and the specific gravity was converted into Balling degrees by reference to Table I1 of the A. 0. A. C. methods (4).
01).
Hgh Power Rehy
ELECTROLYTIC SHERRY TEMPERACOOKERWITH ELECTRICAL TURE CONTROLLER
FIGURE 2.
FIGURE 1. SCHEMATIC DIAGRAM OF ELECTROLYTIC SHERRY COOKER
The electrolytic production of rancio flavor has been investigated in some detail, and the results obtained from the point of view of oxidative changes are reported, together with the results of other studies on the oxidative phases of sherry making.
Experimental Procedure The methods used for the analyses of wine were, with the exceptions enumerated, those of the A. 0. A. C. (4). TOTAL ACIDSwere determined by titrating 5 cc. of wine diluted with 100 cc. of hot distilled water with 0.1 N sodium hydroxide, using phenolphthalein indicator. The results are expressed as grams of tartaric acid per 100 cc. of wine. VOLATILE ACIDSwere determined by steam distillation, usin a modified micro-Kjeldahl apparatus taking over 100 CC. of distillate at about 60' C. in the course of 10 minutes and titrating hot. The results are expressed as grams of acetic acid per 100 cc.
TANNIN was determined in the early samples on 10 cc. of wine plus 20 cc. of indigo by the A. 0. A. C. method. Subsequent determinations were made using 5 cc. of wine plus 5 cc. of indigo, and titrating in an 800-cc. beaker after the addition of 500 cc. of water. The end point was more easily determined in this case, but the results obtained were the same as by the official method. ACETALDEHYDE was determined by a modified Ripper method (SS),using the precautions given by Kolthoff and Furman (47'). PH was determined by quinhydrone and by glass electrode. EH was determined by measuring the potential of platinum wire electrodes in wine under a blanket of carbon dioxide against a saturated calomel cell. Measurements were made a t 25' C., using a Leeds & Northrup glass-electrode-guarded millivolt potentiometer No. 7652, and a Leeds & Northrup type R reflecting galvanometer No. 2500-e with a sensitivity of 3.5 microamperes er minute at 1 meter. Two platinum electrodes were used, a n t the readings were repeated if concordant results were not obtained. A 2-megohm resistance was placed in series with the electrodes t o reduce polarization during measurements and this was fractionally shorted as the electromotive force was balanced (of. Freeman, 18). The readings were reproducible to *5 millivolts. COLOR was measured in a simple Lovibond tintometer at a depth of 4.3 cm. (10 cc. of wine in a Rat-bottomed tube, 1.6 cm. i. d. and 1.8 0. d.) using Bureau of Standards standardized glasses (blue, 1180 NT; red, 200 NT; yellow, 510 NT, 19). CONDUCTIVITY measurements were made with a Leeds & Northrup portable 60-cycle eIectrolytic conductivity bridge No. 4960, using a dipping conductivity cell with circular platinized electrodes 1.6 cm. in diameter set 2.5 om. apart. ELECTRICAL SHERRYCOOKER.The electrical cooker used in the preliminary tests consisted of a small oak cask fitted at the bottom with two carbon electrodes. To avoid several obvious disadvantages of such an apparatus, a special cooker was constructed of glass-lined steel, as shown in Fi ures 1 and 2. This consists essentially of a round-bottom cylinfrical shell, 14 inches in diameter and 17 inches high, having a capacity of 10 gallons. The heating element consists of two graphite rods, 6/8 inch in diameter, set in rubber which was sealed externally with melted sulfur. These electrodes were inserted so that they were about 1 inch a art. The temperature in the cooker was controlled by a high-guty Rotax electrical controller, set usually a t 135" F.
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INDUSTRIAL AND ENGINEERING CHEMISTRY
(57.2" C.), which controlled temperature by making or breaking the circuit attached to the graphite rod. When the cooker was fully char ed, the temperature was maintained constant within *0.5'F. f+0.28" C.). Electrolysis occurred during the heating period of about 3 hours necessary t o bring the wine up to temperature, and at intervals thereafter in maintaining this temperature. The cooker was not insulated against heat loss; therefore, frequent short eriods of heating occurred during the course of the experiment. ~ ~ e c t r o ~ ycould s i s be reduced by using a larger and better insulated tank.
573
Quercyl, Tannol, and Cognac, were not found to be as satisfactory as the white oak &ips.
Effect of Acetaldehyde Addition and Forced Oxidation
Since it has been found that acetaldehyde is one of the flavoring constituents of sherry, it was thought that the addiit some tion of acetaldehyde to sherry material might give rancio characteristics. Varying amounts of acetaldehyde from 5 to 500 mg. per liter were added to Tokay sherry maEffect of Oak and Air on Flavor terial. The sharp flavor of acetaldehyde was perceptible at 10 mg. per liter and became objectionable at 50 mg. per liter. Preliminary investigations were made to determine the Even on prolonged storage the acetaldehyde did not blend effect of extent of aeration and presence of oak chips on the with the wine and merely exaggerated its raw brandy flavor. development of sherry flavor. Sherry material prepared from The addition of acetaldehyde to finished sherries had a Tokay grapes a t a Lodi winery was heated a t 140" F. in tendency to bring out a brandy flavor although the aroma of crown-capped quart bottles which were filled so that, after the wine was improved. Some loss of acetaldehyde occurred the wine came up to temperature, the head spaces left in the during storage but a t a rather slow rate. respective bottles would be a t several predetermined values. The addition of hydrogen peroxide to sherry material reThe results summarized in Table 111 show that oxygen dissulted in a rapid formation of acetaldehyde but gave the solved in sherry material is not sufficient to produce the wine an unpleasant oxidized flavor even when added a t cbncentrations of 50 mg. per liter. Apparently the addition of acetaldehyde or TABLE111. EFFECTOF AMOUNT OF AIR ON DEVELOPMENT OF rapid oxidation with hydrogen peroxide does FLAVOR AND ON ALDEHYDE CONTENT OF SHBRRY not give the true rancio flavor produced by Flavor and Color AcetHead normal oxidation of the wine. 7
Space Per Cent
0.0
After 1 mo. a t 140" F.
After 2 mo. at 140" F.
.aldehyde
Mg./liter
No change in color, raw flavor, cooked odor Little change in color and flavor but a somewhat cooked odor Same as above
Increase in cooked flavor; no change in color Increase in color, flavor somewhat burnt
20.0
Tests with Electrical Cooker LODITOKAY SHERRY MATERIAL.Freshly pre-
pared sherry material of the 1935 vintage, not stored or shipped in oak, was heated in the electrolytic sherry cooker previously described. The .Increase in color, some pre41 4 10.0 temperature was raised from 68" to 130" F. (20" cipitation, more sherry flavor to 54.4" C.) during the course of 3 hours and Bitter rancio flavor approach48.4 20.0 Slight increase in color and a was then maintained a t 130" E'. Samples (1 ing commercial samples little rancio flavor A good amber color and some 66.1 40.0 Developed rancio flavor and quart) were withdrawn periodically a t the inoxidized flavor, deposit golden yellow color tervals shown in Table V and were stored a t Flat oxidized flavor but still Oxidized flavor, dark color, 78.0 50.0 room temperature in completely filled sealed rather raw in taste cloudy, deposit I bottles. The cooker was operated continuouslv. exceDt for the Deriod from Januarv 9 to ii, 193k. The heiting was discontinGed January 28 because a t that time the sherry material had a desired color and flavor, and that both the development of rancio flavor and the darkening of color are largely oxidative satisfactory amber color and a decided sherry or rancio odor. After cooling to room temperature, the sherry was divided processes. Too much oxygen, however, results in the formation of undesirable flavors. The aldehyde content in the into three lots; to one was added 9 grams per liter of dried wines increased with increase in head space. The relatively green walnut hulls (W), to another 9 grams per liter of white high aldehyde content in the control was due to the fact oak chips (0),and to the third no addition was made. The that it was opened and left partly filled for several days before samples were stored in stoppered 5-gallon carboys for 3 analysis. Tests have shown that the heated wines form weeks a t room temperature, and then filtered and bottled. aldehydes rapidly on exposure to air [compare Trillat (43) and Laborde (29)1. I n another series of tests the same sherry TABLEIV. EFFECTOF OAKCHIPSON FLAVOR AND ALDEHYDE CONTENT material was heated in sealed bottles with IN WINES HEATED AT 140" F. WITH A 40 PER CENT HEADSPACE head spaces of 20 and 40 per cent, respectively, in the presence of added oak chips. Oak Flavor Content After 1 month After 2 months Aldehyde These chips were added by weight in various Per cent Mg. /liter quantities up to 0.2 per cent. The oak chips were found to improve the flavor of the sherries 0.0 Somewhat oxidized but Oxidized flavor, somewhat too 100 slightly raw and harsh strong of aldehyde m a r ked 1y , b u t t h e optimum concentration 0.01 More mellow than above About like the above 10% varied from 0.02 to 0.05 per cent, depending 0.02 Mellow with an agreeable A fair rancio flavor with good 11% on head space and length of heating period. sherry taste ash flavor It was believed that the oak chips might cata0.05 Quite mellow rancio flavor Bitter oak flavor but not so 106 but somewhat too oaky pronounced as a t first lyze t h e f o r m a t i o n of a c e t a l d e h y d e in a 0.10 Mellow flavor, no brandy Bitter oak flavor but not so 107 manner somewhat similar to that induced by harshness but too oaky in pronounced as a t first sugi wood in which sake is aged (5'0, @). Howflavor ever, as the results shown in Table IV indi0.20 Excellent aroma but too Too much oak flavor, masks 104 strong in oak flavor everything else cate, no such effect was observed. Charred or toasted oak chips and extracts of oak, such as 5.0
40.0
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INDUSTRIAL AND ENGINEERlNG CHEMISTRY
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A blending of the flavor of brandy with that of the wine occurred quite early in the heating process. Even after 3 days the wine had lost its original raw brandy flavor. TULAREMUSCATSHERRYMATERIAL.Sherry material, which consisted largely of fortified dry muscat but to which caramel sirup had been added, was stored in a 10-gallon oak keg for about a month and then heated in the cooker. The controller was set a t 140' F. About the same time a finished sherry wine, prepared a t the winery from similar sherry matkrial, was also cooked to determine whether its flavor could be improved SHERRY MATERIAL by a finishing treatment in the electrolytic heater. TABLEV. CHANGES IN COMPOSITION OF LODITOKAY Time Both wines were of the 1935 vintage. The In Total Volatile AldeSample Heater Alcohol Extract Acid Acid Tannin hyde PH EH initial current input in the sherry finishing test Dags Vol. % ' --Grams per cc.Mg./Ziter MU. was 3.4 amperes, and the initial temperature of 1/2/36 0 21.2 4.65 0.432 0.090 0.029 21 .. ... the sherry was 68' F. (20' C.). The current in4 20.8 4.64 0.384 0.089 0 031 7s .. ... 1/6/36 creased rapidly 6s the temperature of the wine 1/9/36 7 20.8 4.61 0 . 3 6 8 0.0895 0.029 83 .. ... 1/17/36 12 20 6 4.61 0.345 0.090 0.029 97 .. . . . rose; it was 4.8 amperes a t 100.5" F. (38' C.) 1/24/36 19 20.5 4.58 0,336 0 090 0.033 132 .. ... and finallv became 6.5 amDeres when the sherrv Sh 23 20.4 4.57 0 327 0 090 0.031 135 .. ... reached the temperature o-f 130" F. (54.4' C:) 23 19.6 4.59 0 323 0,087 0.053 135 .. .. W 0 23 19.2 4.58 0.323 0.087 0.040 130 :1: a t which it was cooked. The conductivity of the sherry material was higher at the higher s-1 ,. 21.2 2.40 0,186 0.0161 48 3.59 +232 s-1-0 .. 19.2 4.44 0 : 295 0,092 0.0365 166 4 , io + 124 + temperatures; thus the initial current consumpS-1-W . . 2 0 . 1 4 . 4 6 0 , 3 0 6 0 . 0 9 2 0 . 0 4 9 0 102 4 . 1 5 tion was a t 4.5 amperes a t 68' F. and 8.5 ams-1-s ,. 20.4 4.60 0.314 0.094 0.0342 174 4.10 peres a t the final temperature of 140' F. I n both cases the line voltage fluctuated between 112 and 116 volts. As in previous tests about color and had a pleasing sherry aroma. However, in taste 3 hours of heating were required to attain cooking temit was rather sharp and acrid, somewhat resembling the flavor perature. Samples of about 1 gallon were withdrawn periodiof wine to which acetaldehyde had been added. The addition cally during heating. These were stored in sealed bottles of oak chips modified this flavor somewhat and improved the a t room temperature and analyzed after 12 months, with aroma, but dried walnut hulls gave the sherry a rather unthe results shown in Table VI. pleasant "green" flavor that was not desirable. During The electrical treatment again resulted in a rapid blending storage in the bottle the flavor of the sherry gradually imof flavor of the alcohol with that of the wine and in the rapid proved without loss of rancio odor; and after 16 months it formation of aldehyde flavor. The sherry was too light in had a rather agreeable taste, particularly if treated with oak. color at the conclusion of the test and did not have the deIt was, however, too thin in body as a result of the use of a sired taste. The sherry was improved in flavor after treatpoor grade of grapes in preparing the original sherry mament for 3 days but, when stored, acquired an off-flavor due terial. to its previous treatment with caramel. The decrease in Durilig storage in the bottle the filtered sherry became fixed acidity, so pronounced in previous tests, was not encloudy and deposited sediment. This occurred in both the countered in this sherry material, although there was a filled and partly filled bottles, although more rapidly in the definite downward trend in the sherry. The oxidationlatter. This clouding and precipitation reoccurred after reduction potential increased in the sherry but decreased the removal of the material already thrown out of solution, even after several filtraTABLEVI. CHANGES IX COMPOSITION OF TULARE SHERRYMATERIAL AND SHERRY tions. This clouding was preDURING ELECTROLYTIC COOKING vented, however, by the addi---Sp. Gr tion of 50 p. p. m. of sulfur DealcoTime holized Total Volatile Aldedioxide which also reduced the Sample Heated Wine wine Alcohol Extract Acid Acid Tannin hyde pH EH aldehyde flavor considerably. Days Vot. % Grams per cc. . Mg./liter Mu, Table V shows that the alSherry Wine dehyde content of the wine 1,0158 19.2 S-2-1 0 0.9918 4.16 0.422 0,067 3.85 120 0,0509 52 5-2-2 19.1 4.14 0.418 0.066 1 0,9919 1.0156 0.0615 81 3.86 131 increased rapidly during the 5-2-3 20.0 0.068 3 0.9919 1,0155 4.08 0.406 3.87 168 0.0612 100 heating period, finally reach20.0 0.400 0.069 4 0.9919 1.0156 4.13 3.88 216 S-2-4 0.0584 114 ing 135 p. p. m. At the same Sherry iMateria1 time an appreciable decrease 3.79 231 1.0114 19.0 0.651 0.165 0.0437 22 3.08 0 0.9890 S-3-1 1 8 . 6 3.44 0.378 0,058 4.06 190 4 0 , 9 9 0 3 1.0132 0.0478 88 S-3-2 in fixed acids occurred. On 184 100 4.09 18.5 3.44 0,393 0.057 0.0526 6 0,9903 1,0129 9-3-3 prolonged storage the aldehyde 0.064 120 3.42 0.382 92 4.07 18.5 0.0417 8 0,9904 1.0132 9-3-4 content increased somewhat, except in the sample treated with walnut hulls in which a in sherry material. Both lots remained clear after filtradecrease occurred. A slight loss in alcohol occurred during tion and bottling and did not cloud as did the Tokay heating. The low alcohol content of the samples treated with sherry material. The storage in oak before heating may oak chips and walnut hulls was due to evaporation after heathave influenced this behavior. I n several other instances, ing. The sample of the original sherry material (S-l), stored storage in oak long enough to absorb some oak extracin the original gallon glass bottle in which it was received, intives reduced the tendency of the wine to cloud after treatcreased in volatile acidity, probably as a result of contaminament. tion although none of the other samples showed this effect.
The samples were analyzed about 30 days after withdrawal and then again after storage for 16 months (S-1 series) with the results shown in Table V. The aldehyde flavor increased rapidly during heating, becoming quite pronounced after 7 days. However, a t that time the sherry was still light in color and did not have the necessary caramelized flavor. After the sherry had been heated for 23 days, the finished product was light amber in
J
izg
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r
M A Y , 1938
IRDUSTRIAI, AND EXGINEERING CHEMISTRY
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CARIGNANE SHERRY MATERIAL FROM 1,ODI. Sherry material made commerciaUy from Carignane grapes a t Lodi were used in another test. The grapes were pressed immediately after crushing, and the resultimgmust was aerated before fermentation to decrease further its anthocyanin pigment content. The sherry material was filtered before being heated in the electric cooker. The resistance of this wine was rather high; a t 68' F. and 118 volts, only 2.5 amperes were drawn, and the current increased to only 5 amperes when the heater attained cooking temperature (137O F., or 58.3" C.) after about 4 hours. One-quart samples were withdrawn periodically and stored in sealed bottles at room temperature. A t the same time the same sherry material was heated in a 30,000-gallon redwood vat in the winery with steam-heated copper coils. The heating a t the winery was begun several days before the first sample (S-51) was withd r a m , but the wine had reached only 118" F. (47.8" C.). Samples of this sherry material were withdrawn periodically and shipped by express to Berkeley where they were stored a t 36' I". (2.2' C.) until analyzed. Ai1 samples were analyzed together about 4 months after the last sample was received. The analyses are shown in Table VII. When the final sample of the electrically heated sherry was withdrawn, the remainder was stored in a &gallon oak keg for some 6 weeks and then filtered and bottled. The storage period in oak was found to be somewhat too long as the wine had a strong oak flavor. It also had a tendency to cloud. This wine was divided into several lo&; to one lot, 0.005 per cent tannic acid was added to improve the flavor, another was clarified with gelatin, and to the remaining three portions were added 50,100, and 200 p. p. m. of sulfur dioxide, respectively. The sulfur dioxide immediately masked the aldehyde flavor and markedly reduced the sharp oak flavor. However, at 100 p. p. m. it was apparent to taste and at 200
coiiriesy, P d l i w i n e company
A SHERRY BAKINQTANK
INDUSTRIAL AND ENGINEERING CHEMISTRY
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p. p. m. became objectionable. The sulfur-dioxide-treated samples remained clear even when stored in partly filled bottles, although some of the untreated samples clouded, The samples clarified with gelatin also remained clear. The data shown in Table VI1 indicate that the fixed acid content decreases during electric heating with a corresponding increase in pH. A marked increase in aldehyde content occurs. To determine whether oxidation of any other constituents occurred, 5-cc. samples of the wine, untreated, after dealcoholization, and after dealcoholization and decolorization with charcoal, respectively, were titrated with 0.0412 N potassium permanganate in the presence of 5 cc. of indigo carmine. The blank titration of indigo carmine was 5.55 cc. The volume of permanganate solution necessary to oxidize substances more readily oxidized than indigo is shown in Table VII. Apparently there was but little change in these substances during heating. The oxidation-reduction potential varied in a rather erratic manner and was not related to the acetaldehyde content. This may be due to the fact that it was not determined directly on the samples immediately after they were taken. However, the first sample withdrawn for analysis from the sealed bottles was measured for oxidation-reduction potential. The color of the samples increased during heating but not as rapidly as did the aldehyde content. The final samples were rather light in body, resembling the fino sherries in this regard. They also resembled the latter in aroma but not in flavor. The sherry heated in the winery increased in extract content and in aldehyde content during heating, but otherwise remained practically unaltered in composition. A slight increase in color occurred. The color of several commercial sherries measured in the same way varied from 7.0 to 13.5
VOL. 30, NO. 5
tempemtux- "C.
ELECTRICALRESISTANCEOF SHERRY WINEAS AFFECTED BY TEMPERATURE FIGURE 3.
Included in Table VI11 are the analyses of three samples of sherry produced by the electrolytic treatment in a winery. These samples were heated in lots of several I , hundred gallons each: the sherry material was circulatedfrom a glasshined vat through an elecTABLEVIII. CHANGES IN COMPOSITION OF LIVERMORE VALLEY tric heating unit of about 30 gallons capacity. DURING COOKING SEMILLON SHERRY MATERIAL Samples 5-7-2 and 5-7-3 were heated longer -Sp. Gr.-Dealcohol- AlooEx- Total Volatile 41deand their aldehyde content was correspondingly Sample Wine ized wine hol tract Acid Acid Tannin hyde pH EH Vol. % --Grams per cc.-Mg./Ziter Mu. higher than that of S-7-1. All three sherries S-6 0.9831 1.0087 20.3 2.18 0.522 0,054 0.0428 13 3.30 289 had an aroma, but were thin in body S-6-0 0.9832 1.0085 20.3 2 . 1 0 0 . 5 1 2 0 . 0 3 6 0.0444 70 3.47 358 and lacked the nutty flavor of well-aged SamS-6-P 0,9831 1,0085 2 0 . 4 2 . 2 2 0.487 0 , 0 3 7 0.0444 60 3.80 366 5-7-1 0,9934 1.0177 19.0 4 . 8 0 0 . 4 9 2 0.064 0.0474 60 3.70 210 ples of sherry. S-7-2 S-7-3
0,9956 0,9930
1,0121 1,0178
19.5 20.4
5 . 4 0 0 . 3 9 6 0.049 4 . 6 8 0.351 0.044
0.0308 0.0294
132 112
3.89 3.88
164 151
Electrolytic Resistance of Wine units of red a t a level of 20 units of yellow. After some 50 days of heating, the acetaldehyde content was not as high as that found for samples heated electrically for 3 days. The final sample was not as mellow and still had a raw brandy taste. This was not present in the electrically heated sherries. A blend of the two lots had an acceptable sherry flavor, superior to the average commercial sherry on the market. SEMILLON SHERRY MATERIAL.A dry Semillon wine containing 200 p. p. m. of sulfur dioxide was obtained from a Livermore Valley winery. The alcohol content of this wine was increased from 11 to about 20.5 per cent by the addition of absolute alcohol. A sample of the fortified wine was held as a check (S-6), and the remainder was heated at 138" F. for 5 days; the amperage increased from 2.5 a t 68" F. to 4.9 a t 138" F. One lot of this sherry was stored in glass (S-GP), and the other was stored in an oak keg for 1 week and then transferred to glass (S-7-0). The analyses are given in Table VIII. In spite of its high sulfur dioxide content, a definite aldehyde flavor and a rancio aroma were produced. However, the flavor of the resulting sherry was not so good as that prepared from other lots of sherry material, and it lacked the color and body of a commercial sherry.
The current consumption during the initial heating periodincreased rapidly as the wine was heated and practically doubled as the temperature increased from 68" to 140" F.
TABLEIX. COMPARISON OF INCREASE IN CONDUCTIVITY OF SHERRY AND POTASSIUM CHLORIDE WITH RISE IN TEMPERATURE -------Resistance Temperaturea O
c.
10 15 20 25 30 35 40 45 50 55 60 65 70 75 80
0.02M
KC1
in Small Conductivity Cell-
Ohms
S-4-1 Ohms
162' 147 133 122 112.7 104.5 96.8 90.8 85.2 80.4 75.6 71.5 68.0 64.8
224 193.4 167 147 131 118 109 98.5 89.7 83.2 77.5 72.0 67.2 62.2
Ohms
...
Actual readings at temperaturea oases. 0
6-4-9 260 220 190 164 145 129 116.3
...
95
... ...
79 68
59:7 A
S-5-1 Ohm%
...
241 208 181 160 142 128 115.4 105 96 87.5 81 75.3 70 65.5
S-5-9 Ohms
...
226 195.5 169 149
... ...
119 98
... ... 70.7 ...
82.5
61.5
0.lo C. from these levels in certain
MAY, 1938
INDUSTRIAL AND ENGINEERING CHEMISTRY
This increase in amperage was thought to be due to decrease in resistance of the wines with rise in temperature. I n order to determine how this change compared with that of a simple electrolyte, the conductivity of several samples of sherry wine was measured in comparison with that of an 0.02M solution of potassium chloride. The results (Table IX and Figure 3) show that the conductivity of wine increases more rapidly with increase in temperature than does that of potassium chloride, probably because of the higher viscositytemperature coefficient of wine. Heating the sherry material increases its Conductivity as can be seen by comparing sample S-4-9 with S-4-1 and 5-5-9 with 5-5-1.
Summary and Conclusions The production of sherry flavor in wines has been discussed in a general manner. The rancio flavor is due in part to acetaldehyde or to products derived from it. In order to develop this flavor, it is necessary that some oxygen be present in addition to that dissolved in the wine. A method of rapidly increasing the aldehyde content of wine by electrolytic heating has been described. This method not only increases the aldehyde content, but also brings about a rapid blending of the brandy and wine. The addition of sulfur dioxide has been found to improve the flavor of harsh tasting wines, largely by reducing their free aldehyde content. This also stabilizes sherry wines against clouding. Electrolytic treatment of sherry material a t 130 O to 140 O F. (54’ to 60” C.) with a 60-cycle a. c. current results in too rapid an aldehydrification when conducted as described here. The rate of aldehyde formation may be reduced by currents of higher frequency or by external heating in addition to electrolysis. The method may be applied in practice by using a small electrical treating unit in conjunction with a large storage vat in which the temperature is maintained by hot water coils and by circulating the sherry from the vat through the treating unit. Electrodes may be placed in tanks of larger size and the sherry material circulated by an external pump. The effect of changing the frequency of the current and of changing the size and kind of electrodes is being investigated.
Acknowledgment The analytical data were obtained largely by Elmer Phillips, Fred Henriques, Coleman D. Wilder, Harold Smith, and Rayburn Dunn under the supervision of the writer. (Rayburn Dunn is a worker on Works Progress Administration Project No. 5456, Official Project a t the University of California, Eighth District.) The writer is indebted to the National Carbon Company for the electrodes, to the Pfaudler Sales Company for the electrical sherry cooker, apd to the Foxboro Company for the Rotax temperature controller. He desires to take this opportunity to express his appreciation to the several wineries which cooperated by furnishing samples of wine for treatment and analyses, particularly Shewan-Jones, Inc., and Woodbridge Vineyard Association of Lodi and the Tulare Wine Company.
Literature Cited (1) Allen, H. W., “Romance of Wine,” Chap. VI, pp. 134-63, New York, E. P. Dutton and Co., 1932. (2) Allen, H. W., “Sherry,” London, Constable and Co., 1933. (3) Anonymous, Wine Rev., 3, No. 5, 2 1 (1935). (4) Assoc. Official Agr. Chem., Methods of Analysis, 4th ed., pp 163-9 (1935). (5) Berti, L. A., W i n e Rev., 4, No. 2 , 10-12, 24 (1936). (6) Bioletti, F. T., Calif. Agr. Expt. Sta., Bull. 167, 1-66 (1905); 213, 395-442 (1911).
577
Ibid., Rept. of Viticultural Work during Seasons 1887-93, pp. 296-337 (1896). Brown, E. M., and Henriques, V. de F., IND.ENG.CHEM.,27, 1235-40 (1935). Castella, F. de, J . Dept. Agr. Victoria, 7, 442-6, 515-28, 577-83, 621-30, 724-7 (1909); 24, 690-8 (1926). Cetti, Carlo, Calif. W i n e Rev., 3, No. 1, 12-13 (1935). Charles, E., Ann. fals.,23, 1 5 3 4 (1930). Crampton, C. -4., U. S. Dept. Agr., Div. Chem. Bull. 13, 31965 (1887). Cruess, W. V., Wine Rev., 5 , No. 1, 14-16, 36-7; No. 2, 12-14, 2 0 ; NO. 5 , 14-16 (1937). Cruess, W. V., and Joslyn, M. A., Fruit Products J . , 13, 365-6 (1934). Estallela, J., Anales SOC. espafiol. fh.quim., 21, 3 3 4 4 (1923). Fain, J. M., and Snell, F. D., IND. ENG.CHEM.,News Ed., 12, 120-1 (1934). Filandeau, G., Ann. fals., 2 , 82-4 (1909). Freeman, M. E., Science, 83, 562 (1936). Gibson, K. S., and Harris, F. K., Bur. Standards, Sci. Paper 547, 1-46 (1927). Higasi, Tuneto, Bull. Inst. Phys.-Chem. Research (Tokyo), 8 , 831-8 (1929); Abstracts 2, 97.
Hochwalt, C. A., Thomas, C. A., and Dybdal, E. C., IND. ENG. CHEM.,27, 1404-7 (1935); Trans. Am. Inst. Chem. Engrs., 31, No. 4 , 686-97 (1935); (to N. S. Talbott) U. S.Patents 2,027,099, 2,027,100, and 2,027,129 (Jan. 7 , 1936). Jaulmes, P., and Espesel, P., Ann. fals., 28, 325-35 (1935). Joslyn, M. A., Fruit Products J., 13, 208-10, 2 4 1 4 (1934). Ibid., 13, 326-31 (1934). Zbid., 15, 10-12, 24 (1935). Joslyn, M. A., Marsh, G. L., and Fessler, J., J . Assoc. Oficiat Agr. Chem., 20, 116-30 (1937). Kolthoff, I. M., and Furman, N. H., “Volumetric Analyses,” Vol. 2, pp. 450-2, New York, John Wiley & Sons, 1929. Kosak, Josef, Chem. Obzor., 10, 49-50 (1935). Laborde, J., Rev. vib., 48, 225-30, 241-4, 386-90 (1919). Lachman, Henry, U. S. Dept. Agr., B u r . Chem. Bull. 72, 25-40 (1903).
Marquis, H. H., Wine Rev., 4, No. 6, 6-7, 2 2 (1936). Muller-Thurgau, H., and Osterwalder, A., Landw. Suhrbuch. Schweiz, 28, 480 (1914); 29, 408 (1915). Ripper, Monatsh., 21, 1079 (1900). Roques, X., Rev. vit., 12, 95-9 (1899). Zbid., 19, 260-1 (1903). Ibid., 19, 501-5, 570-3, 594-8 (1903). Sannino, F. A., “Tratado de Enologia,” tr. from Italian into Spanish by Arnesto Mestre, pp. 354-9, Barcelona, Gustavo Gila, 1925. Schanderl, Hugo, Wein u. Rebe, 18, 16-26 (1936). Smith, Clifford, Rept. Third Wine Conference a t Univ. Calif., mimeographed by Wine Inst., 1935. Thudichum, J. L. W., “Treatise on Wines,” Chap. XXII, pp. 226-304, London, George Bell and Sons, 1894. Thudichum, J. L. W., and Dupr6, August, “Treatise on Origin, Nature and Varieties of Wine,” Chap. XX, pp. 623-72, London, Macmillan and Co., 1872. Tomoda, Yoshinori, S.SOC.C h m . Znd. J a p a n , 39, Suppl. binding 56 (1936). Trillat, A., Ann. inst. Pasteur, 22, 704-19, 753-62, 876-95 (1908).
Trillat, A., Rev. intern. fals.,21, 72 (1908); Compt. rend., 146, 645 (1908); Bull. S O C . chim., 5 , 555-8 (1909). Twight, E. H., Wines and V i n e s , 17, No. 4 , 5, 15 (1936). Wetmore, C . A., Appendix B to Rept. of Calif. Board of State Viticultural Commissioners for 1893-94, Sacramento, 1894. Wiley, H. W., “Beverages and Their Adulteration,” pp. 233-9, Philadelphia, P. Blakiston’s Son and Co., 1919. Wiley, H. W., U. S.Dept. Agr., B u r . Chem. Bull. 72, 1-24 ( 1 9 0 3 ) . Yamada, M., J . Agr. Chem. SOC.J a p a n , 6. 168-77 (1930); BdZ. Agr. Chem. SOC.J a p a n , 6, 9-11 (1930). RECFOIYED October 28, 1937.
